remove mul_unorm8/mad_unorm8
I just kind of remembered that if we're doing (xy+x)/256
and x is a destination channel and y is 255-sa, then you
can get the +x for free by multiplying by 256-sa instead.
(d * (255-sa) + d)
(d * (255-sa + 1))
(d * (256-sa) )
Duh. This is a trick we play in a lot of legacy code and
I've just now realized it's exactly equivalent to the trick
I want to play here... sigh.
Folding this math in kind of makes mul/mad_unorm8 moot.
Speed's getting good:
I32_SWAR: 0.3 ns/px
I32 : 0.55 ns/px
F32 : 0.8 ns/px
RP : 0.8 ns/px
Opts : 0.2 ns/px
Change-Id: I4d10db51ea80a3258c36e97b6b334ad253804613
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/220708
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
5 files changed